Maybe you can order a black zentai suit online and then free-hand undersuit detailings using either craft foam, thin EVA foam floor mats, or upholstery foam. It's tricky to do an undersuit without adequate references or files to work from, but to get the size right you could even make a mock up dummy bust to draw the undersuit designs on and work from there! I want to make parts of an undersuit for my mark iv (mostly thighs and torso being the most visible) but haven't got around to it yet.
Best of luck! Always good to see more CE Chiefs